core: arm: plat-versal: Add maybe_unused attribute to constant strings

If log level is set to print only EMSGs, constant strings can be unused.
Add maybe_unused attribute to prevent compilation errors.

Signed-off-by: Sriram Sriram <sriramsriram@microsoft.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>

core/arch/arm/plat-versal/main.c

@@ -62,8 +62,8 @@ static TEE_Result platform_banner(void)
 {
 	vaddr_t plm_rtca = (vaddr_t)phys_to_virt(PLM_RTCA, MEM_AREA_IO_SEC,
 						 PLM_RTCA_LEN);
-	const char *ahwrot_str = "OFF";
-	const char *shwrot_str = "OFF";
+	const char __maybe_unused *ahwrot_str = "OFF";
+	const char __maybe_unused *shwrot_str = "OFF";
 	uint8_t version = 0;
 
 	assert(plm_rtca);